Diagnostic criteria, formulated by the IMWG (International Myeloma Working Group), update 2016:

 

Symptomatic Myeloma:
 
Both criteria must be met:

1 ≥ 10% clonal plasmacells in bone marrow or extramedullary localisation.

2 any one or more off the following CRAB criteria and myeloma-defining events (MDE):

CRAB:

C Hypercalcemia: serum calcium >2.75 mmol/L).

R Renal insufficiency: serum creatinine >177mol/L or creatinine clearance >40 mL per minute.

A Anemia: hemoglobin valure of >20g/L (>1,25 mmol/L) below the lowest limit of normal, or a hemoglobin value <100g/L (<6,3 mmol/L).

B Bone lesions: one or more osteolytic lesion on skeletal radiography, CT, or PET/CT.***

MDE:

≥ 60% clonal plasmacells present in bone marrow.

Free Light Chain (FLC) involved / uninvolved ratio ≥ 100 and absolute FLC of involved light chain ≥ 100 mg/L
   (involved light chain -either kappa or lambda- is the one that is above the normal reference range;
   the uninvolved light chain is the one that is in or below the normal range).

More than one focal lesion on MRI that of ≥ 5mm in size.

 

Smoldering Multiple Myeloma:
 
Both criteria must be met:

1 Serum M-protein (IgG or IgA) ≥ 30 g/L and/or 10-60% clonal plasmacells in the bone marrow.

2 Absence of MDE or amyloidosis

 
Non-IgM monoclonal gammopathy of undetermined significance (MGUS):
 
All three criteria must be met:

1 Serum M-protein (IgG or IgA) ≤ 30 g/L.

2 Clonal plasmacells in the bone marrow ≤10%

3 No CRAB criteria or amyloïdosis

 
IgM MGUS:
 
Both criteria must be met:

1 Serum IgM M-protein ≤30g/L.

2 No evidence of anemia, constitutional symptoms, hyperviscosity, lymphadenopathy, hepatosplenomegaly, or other end-organ damage that can be attributed to the plasma cell proliferative disorder.